Electronic device technology / thermal machine protection


The electronic motor protection relay monitors the winding of electrical machines in conjunction with various temperature sensors. When used correctly, safe protection against thermal overload is guaranteed.

  • Difficult start-up (overload)
  • Excessive switching frequency
  • With rapidly increasing winding temperature due to blocked rotors
  • Phase failure and resulting rise in winding temperature
  • Heating and ventilation
  • Operation with frequency inverters
  • Transformer protection
  • Surface temperature monitoring of power semiconductors
  • High ambient temperature of the sensor up to +200 °C

The trigger device analyses the resistance of a sensor element and calculates the temperature. It is possible to connect PTC, KTY, Pt100 or Pt1000 sensors. The relay is energised in normal operation, i.e. there is no impermissible temperature increase. If an adjustable temperature is exceeded, the relay drops out.
If the temperature falls below the switching threshold, the relay energises again. A predefined switching hysteresis of 5 K guarantees defined switching on and off.
The trigger device recognises a sensor cable break and short circuit, which are signalled via LED. The relays drop out.

  • Adjustable temperature switching point
  • Can be operated with all standard sensors
  • Sensor cable break and short circuit are detected
  • Device operates according to the closed-circuit current principle, i.e. even in the event of a power failure
  • Safe shutdown of the electrical machine
  • Temperature of the motor windings is measured directly
  • Temperature measurement over a wide temperature range
  • Optimum housing dimensions
  • Switching point can be changed by the user at any time
  • Excellent value for money
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